Number of subgroups of index 3 in free group of rank n+1.
A049294
Number of subgroups of index 3 in free group of rank n+1.
Terms
- a(0) =1a(1) =13a(2) =97a(3) =625a(4) =3841a(5) =23233a(6) =139777a(7) =839425a(8) =5038081a(9) =30231553a(10) =181395457a(11) =1088385025a(12) =6530334721a(13) =39182057473a(14) =235092443137
External references
- oeis: A049294